Vapor deposition material support



D 1969 s. R. CZARNOW'SKI 3,486,001

VAPOR DEPOSITION MATERIAL SUPPORT Filed Feb. 5, 1968 Ma i/Vivi.

1:911 fiSyTANLEYRLZARNOM/SKI www i United States Patent U.S. Cl.219--271 8 Claims ABSTRACT OF THE DISCLOSURE A vapor deposition materialsupport for securement to and between the spiral turns of heaterfilament, the support consisting of a planar tungsten shelf held inplace by a tungsten wire clip. The shelf is of the same shape as thespiral filament cross-section, is of larger area than that of the opencross-section withirrthe spiral at the point of securement, and ofsmaller area than that of the overall cross-section of the spiralfilament to thereby form a walled well with a spiral loop of thefilament. The clip is formed of a single piece of tungsten wire bent toprovide three upwardly inturned hooks spaced substantially one hundredtwenty degrees apart about a perimeter substantially the same as that ofthe overall cross-section of the spiral filament at the point ofsecurement. Two of the clip hooks are end hooks formed by. the oppositeends of the tungsten wire and are joined by legs to an intermediatethird hook which is formed up out of the center of the wire by reverselyfolding the wire back next to itself, the two end hooks being otherwiseunconnected to one another. The bight of each of the hooks is largeenough to accommodate the shelf thickness together with the diameter ofthe wire which forms the turns of the heater filament. The shelf and thefilament cross-section illustrated in the drawingsare 'both circular,and the illustrated clip is shown with hooks which lie substantially atthe vertices of an equilateral triangle.

This invention relates generally to the art of thermal evaporation whichis used in industry to coat various materials such as glass, aluminumand steel, and more particularly to the coating of glass, as for examplethe coating of prisms, lenses and mirrors.

A widely used coating material for these applications is pelletizedmagnesium fluoride which is set upon a tungsten shelf inserted betweensuccessive spiral turns of a helically coiled tungsten wire filament,the helical axis being vertically oriented. A vacuum is then drawnwithin the evaporation chamber and the filaments are electricallyenergized to melt and evaporate the magnesium fluoride for depositioncoating of the glass. This process is very chancey, for as often happensthe unsecured shelf slips out from between the filament spirals whichshift due to thermal expansion and contraction, carrying with it themelted magnesium fluoride. When this occurs, the molten magnesiumfluoride falls to the floor of the vacuum chamber and spatters itselfnon-uniformly over the entire charge of glass. This requires that, theprocess be shut down, the chamber be opened and the glass be removed andreprocessed for coating. The probability of such an occurrence is ofcourse multiplied by the number of filaments utilized in a givenchamber, with some chambers having twenty-five or more such filaments.

Many of these articles are worth substantial sums of money and thefinancial loss to a manufacturer can be staggering. By way ofillustration, in coating optics and prisms, a typical coating cycle forthirty prisms would be approximately 16 hours. It has been establishedthat a processor may stand a loss of approximately $600.00 per hour whena shelf falls out of a filament, and as has been pointed out, a shelf islikely to fall at any time during the operation due to vibration orthermally induced movement.

Tungsten shelves and filaments are used because they are substantiallyinert and do not contaminate the processed parts. However, tungsten isnot only hard but is also brittle so that the shelves cannot be bent toprovide a securing means. This has led to the use of tantalum forshelves since this latter material is relatively soft and can bedeformed to secure the shelf to a filament. However, not only istantalum substantially more expensive than tungsten, but much moreimportant is the fact that tantalum outgases when heated and produces ahighly undesirable yellow cast or tint in the coating, resulting in aninferior product. Accordingly, it is a primary object of my invention toprovide a novel clip for quickly and easily firmly securing a metalshelf to and between the spiral turns of a vacuum chamber filament toform a stable support for vaporizable material placed thereon.

Another object of my invention is to provide a novel clip as aforesaidwhich is substantially inert so as to avoid contaminatoin of thevaporizable material.

Still another object of my invention is to provide a novel clip asaforesaid which is simple and inexpensive to make.

A further object of my invention is to provide a novel assembly of theclip as aforesaid and a tungsten shelf which together form a walled wellwith a spiral turn of a heating filament to contain the thermallyfluidized vaporizable material employed in vapor deposition.

The foregoing and other objects of my invention will appear more fullyhereinafter from a reading of the following specification in conjunctionwith an examination of the appended drawing, wherein:

FIGURE 1 is a side elevational view of the clip and shelf according tothe invention secured in operative position to a spiral coil of ahelically wound heater filament;

FIGURE 2 is an enlarged perspective view of the clip and shelf accordingto the invention shown affixed to the heater filament, parts of whichhave been sectioned away for better visibility;

FIGURE 3 is an enlarged plan View of the clip and shelf according to theinvention secured to the filament of FIGURE 1 as would be shown whenviewed along the line 33 of FIGURE 1;

FIGURE 4 is an enlarged fragmentary side elevation of the clip and shelfaccording to the invention being mechanically installed to the helicalfilament;

FIGURE 5 is a vertical sectional view through the installed clip andshelf as would be seen when viewed along the line 55 of FIGURE 3;

FIGURE 6 is a vertical sectional view similar to that of FIGURE 5 buttaken at substantially a right angle thereto and as would be seen whenviewed along the line 66 of FIGURE 5;

, FIGURE 7 is a fragmentary view showing the remaming detail of the endhook engagement as would be seen when viewed along the line 77 of FIGURE3;

FIGURE 8 is a plan view of the metal shelf used in the combination;

nated generally as 20 holding a circular shelf 21 to one spiral loop ofa filamentary heater 22, the heater being formed usually of tungstenwire in the form of a helical coil with a vertically oriented aXis andopposite ends 23 connectable to a source of electrical energization. Asbest seen from FIGURES 2 and 8, the shelf 21 is circular, and as bestseen from FIGURES 1, and 6, the diameter of the circular shelf isgreater than the inside diameter of the spiral loop 24 of the heater 22to which the shelf is secured by the clip 20 while also being less thanthe outside diameter of the same spiral loop.

As best seen from the showing of FIGURES 1 and 2 this results in theformation of a well of which the bottom is formed by the shelf 21 whilethe side walls are formed by the spiral loop 24 to which the shelf isclipped. As is best seen from FIGURES 1, 5 and 6, the shelf 21 isdisposed with its plane not precisely horizontally oriented, but ratherinclined at a slight angle, the inclination of the shelf is such thatthe portion of the spiral loop 24 desingated as 24a in FIGURE 2 spiralsupward away from and out of contact with the shelf 21 on the high sideof the inclined shelf 21. Consequently, as a pellet of the fluidizablecoating material passes from a solid to a molten state, any tendency ofthe molten material to flow across the surface of the shelf 21 is insuch direction due to gravity as to move it away from the perimetrallyunconfined high point edge of the shelf and toward the completely walledregions of the shelf which are gravitically lower. This of courseeliminates any possibility of escape of the molten coating material fromthe confines of the filament walled shelf so long as the shelf 21 isproperly held in position to the filament 22 by the clip 20.

The clip 20 is best seen in the plan view and e1evational showings ofFIGURES 9, and 11 where it is observed that the clip is formed of asingle piece of wire-like material having the opposite ends each formedinto an upwardly inturned book 26, the lower ends of which turnhorizontally in plane into a pair of curved legs 27 which curve inwardtoward one another and turn into substantial parallelism before turningupward and inward to merge with one another and form the intermediatehook 28.

The end hooks 26 and intermediate hook 28 lie substantially on thevertices of an equilateral triangle in the form of the clip asillustrated, although this is not mandatory. The optimum configurationfor the clip is one in which the shelf 21, of whatever geometric shape,is held captive within the clip so that it cannot slip laterallyoutwardbetween any two of the adjacent hooks. Similarly, a

while the shelf 21 is shown as being of circular form, this is sobecause the cross-section of the helically wound filamentary heater 22is circular. The requirement for the shelf 21-is that it shall be ofsufiicient area and proper shape to close the cross-section of theheater to which it is to be secured, regardless of the shape of theheater crosssection. Similarly, the clip configuration is required tosecurely hold the shelf, of whatever shape, to the filamentary heater,again of whatever shape, and to be of such configuration as to permitquick and easy positive securement of the shelf to the heater.

The straight line distance between the end hooks 26 of the clip 20 anddesignated in FIGURE '10 by the dimension B must be less than theoutside diameter of the spiral loop 24 of the heater 22 in theillustrated configuration, and the distance from this base line B to theinside of the intermediate hook 28 designated in FIGURE 3 as A must begreater than the radius of the spiral loop 24. With the clip 20 made ofa springy or resilient material, this results in an installed conditionof the clip where the end hooks 26 are pressing inward against the outersides of the spiral loop 24 at points on the periphery of the latterwhich pull the intermediate hook 28 inward against the spiral. This isbest seen from the showings 4 of FIGURES 3 and 4 to which referenceshould now be made.

As shown in solid line in FIGURE 4, and in phantom outline in FIGURE 3,the clip 20 with the shelf 21 disposed therewithin is positioned so thatthe end hooks 26 bear against the outside periphery of the spiral loop24 with the shelf 21 just underlying the spirial loop 24. Theintermediate "hook 28 is then pressed laterally toward the spiral loop24'as indicated by the arrow 29. The clip end hooks 26 shift laterallyoutward and follow around the periphery of the spiral loop 24 as theintermediate hook 28 moves inward toward and finally against theproximate edge of the spiral loop, the end hooks 26 overriding thediameter of the spiral loop and moving inward again toward one anotherto their final position. The shelf 21 is then held firmly asillustrated.

While the hook20 and shelf 21 are preferably made of tungsten metal, allapplications may not require this, and other suitable materials may beused as long as the previously described design criteria are taken intoaccount.

Having now described my invention in conjunction with a particularlyillustrated embodiment thereof, it will be appreciated that variationsand modfications of my invenion may now occur from time to time to thosepersons normally skilled in the art without departing from the essentialscope or spirit of my invention, and accordingly it is intended to claimthe same broadly as well as specifically as indicated by the appendedclaims.

What is claimed to be new and useful is:

1. A vapor deposition material support comprising in combination,

(a) a heater characterized by the inclusion of a filamentary loop,

(b) a shelf, and

(c) shelf securing means opeartive to secure said shelf to the saidheater filamentary loop, said shelf extending transversely to the saidfilamentary loop and in contact with a substantial part of saidfilamentary loop to thereby form at least a partly walled well with saidfilamentary loop operative to retain molten vapor deposition material onsaid shelf within the confines of said partly walled well.

2. A vapor deposition material support as defined in claim 1 whereinsaid shelf is made of metal and said shelf securing means holds saidshelf in good thermal contact with said heater.

3. A vapor deposition material support as defined in claim 1 whereinsaid shelf securing means comprises a clip having a plurality of hookswhich each extend from a point underlying said shelf upward about theshelf edge and a portion of said filamentary loop.

4. A vapor deposition material support as defined in claim 1 whereinsaid shelf securing means comprises a clip formed of a single piece ofmetal wire bent to provide three upwardly inturned hooks spaced apartabout a perimeter substantially the same as that of the overallcross-section of said filamentary loop at the point of shelf securement,two of said hooks being end hooks formed by the opposite ends of saidwire and joined by legs to an intermediate hook formed from the wire atsubstantially the center of said wire.

5. A vapor deposition material support as defined in claim 1 whereinsaid shelf securing means comprises a clip formed of a single piece ofmetal wire bent to provide three upwardly inturned hooks spaced apartabout a perimeter substantially the same as that of the overallcross-section of said filamentary loop at the point of shelf securement,two of said hooks being end hooks formed by the opposite ends of saidwire and joined by legs to an intermediate hook formed from the wire atsubstantially the center of said wire, said end hooks being unconnectedto one another except by said legs and being resiliently shiftable withrespect to one another, whereby said end hooks may accommodatethemselves to engage a plurality of points about the periphery of saidfilamentary loop.

6. A vapor deposition material support as defined in claim 1 whereinsaid shelf is made of metal and said shelf securing means holds saidshelf in good thermal contact with said heater, said shelf securingmeans comprising a clip formed of a single piece of metal wire bent toprovide three upwardly inturned hooks spaced apart about a perimetersubstantially the same as that of the overall cross-section of saidfilamentary loop at the point of shelf securement, two of said hooksbeing end hooks formed by the opposite ends of said wire and joined bylegs to an intermediate hook formed from the wire at substantially thecenter of said wire, said end hooks being unconnected to one anotherexcept by said legs and being resiliently shiftable with respect to oneanother, whereby said end hooks may accommodate themselves to engage aplurality of points about the periphery of said filamentary loop.

7. A vapor deposition material support as defined in claim 3 whereinsaid clip hooks are spaced substantially equally about the periphery ofa circle, and wherein said shelf is substantially in the form of acircular disc of somewhat smaller diameter than that of the circle aboutwhich said clip hooks are spaced but of larger diameter than thedistance between any two of said clip hooks.

8. A vapor deposition material support as defined in claim 6 whereinsaid shelf and clip are made of tungsten, wherein said clip hooks arespaced substantially equally about the periphery of a circle, andwherein said shelf is substantially in the form of a circular disc ofsomewhat smaller diameter than that of the circle about which said cliphooks are spaced but of larger diameter than the distance between anytwo of said clip hooks.

References Cited UNITED STATES PATENTS 2,980,820 4/1961 Brundige et al.219-354 JOSEPH V. TRUHE, Primary Examiner PETER W. GOWDEY, AssistantExaminer U.S. Cl. X.R. 11848

